1. Field of the Invention
The present invention relates to a color quantization and more particularly, color quantization and method thereof based on hue, max, min, difference (HMMD) color space and a searching method using the same in extracting color features whether or not such features are quantized at same levels or different levels.
2. Description of the Related Art
There are new technologies for searching multimedia based on information. Search engines generally use global and local color information and texture information for image search, and color information plays an important role in image search. As more effective color features are being developed, effective color spaces are needed for such a search.
Color information includes various feature information such as color histogram, local representative color and the like. Accordingly, the search performance greatly depends how to quantize the colors. However, it is not possible to express infinite number of color class when the distribution of color classes is represented on a color space and color quantization is required for representing a color information with the limited number of colors (color classes) by combining similar color groups into a single color label.
For instance, in the case of a color histogram in a RGB color space, each element (R,G,B) in a RGB is represented by a numerical character which ranges from 0 to 255. Thus, color classes amount to 2563 when we consider only integer numbers, which is unrealistic to be represented by color histograms constituted with 2563 bins. Therefore, a single color label is given to consider similar colors one color by grouping them. For the color labeling, a color space is divided into spatial regions amounting to the number of colors to be represented, in which the division method is called a color quantization method.
There are many factors influencing search performance for a multimedia search using colors. First, it is important for a color space to represent colors well. Second, it is important how to divide the given color space because color features of data can be represented or incorrectly depending on the color quantization method. Thus, the color quantization method needs to be proper for high performance search capability.
Further, the related art quantization method does not allow comparison of color information based on different quantization methods or having different quantization levels. All the related arts do not consider the above since the searching is carried on local data bases. Specifically, the comparative search on the color information are based on quantization which is achieved by the same quantization method.
Due to the explosion of internet development and usage, there is a demand for data searching regardless of different data management servers. Therefore, important are functions enabling to compare and search multimedia data reciprocally regardless of the locations and servers of the data. To meet the demands, the proper quantization method should be considered as well as search algorithms for reciprocal comparison, i.e., interoperability, should be provided.